Pressure-sensitive adhesive compositions containing hydroxy-ethyl cellulose

ABSTRACT

An adhesive composition comprising, of the total composition of 100 parts by weight, 90-99 parts by weight on a tacky copolymer of an alkyl acrylate, the alkyl group of which contains 1 to 14 carbon atoms and the average number of which carbon atoms is 4 to 12, with a compound having a double bond and copolymerizable therewith, and 10-1 parts by weight of a hydroxyethyl cellulose.

United States Patent 1191 Ono et al. Dec. 23, 1975 PRESSURE-SENSITIVE ADHESIVE 2,599,576 6/1952 Morris =1 al. 260/17 COMPOSITIONS CONTAINING 3,400,103 9/1968 Samour et a1. 117/122 PA 3,446,767 5/l969 Nolan 260/l7 HYDROXY-ETHYL CELLULOSE 3,535,295 10/1970 Davis et a]... ll7/l22 PA [75] Inventors: Tomoyoshi Ono, l-lino; Yoshihiko 3,684,749 8/l972 Aral et al 260/8 Matsuguma, l-la ghioji both of Ja an 3,725,122 4/l973 Reinh ard ll7ll22 P 731 Assi nee: 'r Limi Osaka, Ja an g cm p Primary ExaminerDonald E. Czaja [221 Flledi 26, 1973 Assistant ExaminerEdward Woodberry 21 APPL 419 05 Attorney, Agent, or FirmSherman & Shalloway [30] Foreign Application Priority Data [57] ABSTRACT 1 Dec 972 Japan 47 127626 An adhesive composition comqnsmg, of the total 52 US. (:1. 260/17 R- 428/535 Pans by 90-99 Pam 511 1m. (1* B32B 23/08; C OBL 1/26 a acrylate' 58 new Search 260/17 R- 117/122 PA- 8MP 1 and the average number of which carbon atoms is 4 to 12, with a compound having a double bond and co- [56] References and polymerizable therewith, and 10-] parts by weight of :1

UNITED STATES PATENTS hydroxyethyl cellulose.

2,027,436 1/1936 Kallander 260/17 3 Claims, N0 Drawings PRESSURE-SENSITIVE ADHESIVE COMPOSITIONS CONTAINING HYDROXY-ETIIYL CELLULOSE This invention relates to adhesive compositions. More particularly, the invention relates to pressuresensitive adhesive compositions suitably used for the preparation of adhesive tapes, adhesive sheet materials or the like, which possess excellent adhesiveness when adhered to an object and, in addition, does not impede the breathing activity of the object to which application has been made.

The adhesive tapes obtained by coating a plastic film, cloth or nonwoven fabric with a pressure-sensitive adhesive composition are also used in the medical field as,-

say, surgical tapes. In the case of an adhesive tape used in the medical field, it is important that it possesses breathability so as not to hinder the ventilation of bodily parts, say, the skin to which it has been applied.

For providing an adhesive tape or sheet material with breathability, a proposal has been made of perforating the conventional adhesive tapes or sheet materials not possessing moisture or gas permeability with numerous minutes holes, and various methods of accomplishing this have been suggested. However, the moisture or gas permeability is limited to only the perforated portions in the case of the adhesive tapes obtained by these suggested methods, and those portions where the adhesive is present is essentially nonpermeable. Thus, these tapes. cannot possibly be considered as being breathable, and the effects obtained by their use are not fully satisfactory. Further, these methods are not economically advantageous, since. there is usually required the extra step of perforation, in addition to the step of manufacturing the adhesive tape.

Again, there has also been proposed a method of preparing a breathable adhesive tape or sheet material by coatinga' porous backing with the usual nonpermeable adhesive in a noncontinuous fashion such as lineally, or'spottily. However, in the case of an adhesive tape having a non-continuous adhesive layer or this kind, there is the drawback that since the area, of'adhesion becomes small, inadequancy of adhesive strength is brought about. Another shortcoming is that the breathing activity is impeded at the portions where the adhesive is present, since the adhesive itself is inherently nonperrneable.

As another method. there is one which proposes the use of a volatile-solvent-containing adhesive in preparing the adhesive tape, the solvent being removed from the adhesive layer by volatilization to impart porosity to the adhesive layer. While this method can beliegarded as excelling the previous two methods in his: this method imparts breathability to the adhesive layer also, there is the disadvantage that complicated steps are required in thatthe adhesive solution is first applied to a liner having a flat strippable surface, after which it is brought to a semi-dried state, then transferred to a porous backing with pressure, and thereafter dried completely.

Further, since in all of these methods holes are formed in the adhesive layer as well as the backing, there is the possibility when these adhesive tapes are used with skin injuries that impurities from the outside might reach the wound and cause its infection.

It is therefore an object of the present invention to provide an adhesive composition in which the continuous layer of a pressure-sensitive adhesive per se possesses breathability.

Another object of the invention is to provide a pressure-sensitive adhesive tape in which the per se breathable continuous layer of a pressure-sensitive adhesive composition is adhered to a gasand moisture-transmissible sheet substrate.

In consequence of our extensive researches with a view to achieving the foregoing objects, we found that by incorporating a small'amount of a hydroxyethyl cellulose in a copolymer consisting predominantly of an alkyl acrylate an adhesive composition excelling in breathability could be obtained without impairment of hardly any of the adhesive properties of the adhesive layer. Thus, the present invention was perfected.

Thus, an adhesive composition is provided by the present invention in which, of the I00 parts by weight of the total composition, the major components cons|st of 99 parts by weight of a tacky copolymer of an alkyl acrylate'whose alkyl group contains 1 to 14 carbon atoms, the average number of which carbon atoms is 4 to 12, with a compound having a double bond and copolymerizable therewith, and I0 1 parts by weight of a hydroxyethyl cellulose.

The use as a pressure-sensitive adhesive of the copolymers consisting predominantly of an alkyl acrylate has been known hitherto, and it is known that these copolymers are superior with respect to their adhesiveness, weatherability and nontoxicity. The pressure-sensitive sheet materials and tapes obtained by coating plastic fi lms, dloths and nonwo ven fabrics with these copolymers are used for medical purposes. In addition, they are used for such purposes as materials for making stationery items, electrical insulation material andindus'trial aterials. However, these copolymers per se do not possess'breathability.

A novel aspect of the present invention resides in'the fact ,that breathability is impartedto the pressure-sensitiiie adhesive by the incorporation of i0 l partsby weight of a hydroxyetliyl cellulose per 100 parts by weight of the total composition.

While the reason why the invention adhesive composition possesses breathability is not entirely clear, it is believed that it is due to the fact that moisture is diffusible via the hydroxyethyl cellulose portion that has been uniformly dispersed in the alkyl polyacrylate copolymer. According to our investigations, even though additions are made of the other compounds similar to hydroxyethyl cellulose, e.g., hydroxypropyl cellulose, carboxymethyl cellulose and sodium polyacrylate, conspicuous results, as in the case where a hydroxyethyl cellulose was added, could hardly be noted. The reason therefor is believed to be due to the fact that because of the lack of hydrophilicity the diffusion of moisture does not take place adequately or the uniform dispersion of the additive throughout the alkyl polyacrylate copolymer does not take place.

When the content of the hydroxyethyl cellulose exceeds l0 percent by weight of the total composition in this case, the adhesive properties, and especially the adhesive force, of the adhesive composition decline. On the other hand, when the content of the hydroxyethyl cellulose is less than I percent by weight, not much improvement can be noted in the breathability of the composition. In either case, this is undesirable, since the resulting produce is inadequate for use as a breathable adhesive composition. Thus, the content of the hydroxyethyl cellulose should preferably be in the range of 3 7 percent by weight of the composition.

The hydroxyethyl cellulose used in this invention as the additive is readily available as a commercial produce (e.g., NATROSOL, a product of Hercules Incorporated, U.S.A.), and it is conveniently used as an aqueous solution of l percent by weight concentratlon.

As the alkyl group of the alkyl acrylate of the copolymer used for adhesive component in this invention, said group containing 1 to 14 carbon atoms can be used, and the average number of the carbon atoms of the alkyl group must be at least 4.

By the expression average number of the carbon atoms of the alkyl group" is meant a value defined by the following equation.

Average number of the carbon atoms of the alkyl group Alkyl acrylates in which the alkyl group has at least 4 carbon atoms are preferred. Examples of these alkyl acrylates are butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate and 2-ethylhexyl acrylate, the 2-ethylhexyl acrylate being especially preferred for its good ability of imparting adhesiveness and also from the commercial standpoint. The acrylic acid esters having lower alkyl groups of less than 4 carbon atoms such as methyl acrylate and ethyl acrylate may also be used by mixing in the like manner, provided that the average number of the carbon atoms in the whole of the alkyl acrylates used is at least 4. When the average number of the carbon atoms of the alkyl group is less than 4, 4, is undesirable, since the resulting copolymer lacks tackiness.

As the monomer to be copolymerized with the aforesaid alkyl acrylates, any monomer that is copolymerizable with the alkyl acrylates will do. Particularly preferred are, however, the polar monomers such as acrylic acid and methacrylic acid; the polyfunctional compounds having at least two nonconjugated carbonto-carbon double bonds in their molecular structure such as diallyl phthalate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolethane trimethacrylate and pentaerythritol methacrylate; vinyl acetate, methyl methacrylate and maleic anhydride.

The polyalkyl acrylates are deficient in their internal cohesive strength and tend to cause cohesive failure of the adhesive layer when used for the preparation of pressure-sensitive adhesive tapes. In this case, when a polar monomer such as acrylic or methacrylic acid is used in a small amount as the monomer to be copolymerized with the alkyl acrylates, the resulting copolymer does not exhibit cohesive failure and is effectively used as the pressure-sensitive adhesive component.

The copolymerization of methyl methacrylate and/or vinyl acetate along with the foregoing polar monomers is also a preferred mode of operation. The methyl methacrylate and/or vinyl acetate is used in an amount of preferably one mole per 5 moles or more of the acrylic acid esters and such a rate that the total of the alkyl acrylate, methyl methacrylate and/or vinyl acetate accounts for 75 95 moles while the acrylic acid LII and/or methacrylic acid accounts for 5 25 moles. Thus, the internal cohesive strength of the copolymer can be further enhanced.

A copolymer obtained by copolymerizing along with the methyl methacrylate and/or vinyl acetate and the polar monomers such as acrylic or methacrylic acid 0.002 0.05 mol% of the composition of the polyfunctional compound, such as mentioned above, is also a very excellent copolymer. in this case the use of poly ethylene glycol dimethacrylate is especially suitable.

The copolymer consisting predominantly of an alkyl acrylate can be readily prepared by the so-called solution polymerization method, i.e., by dissolving the aforementioned alkyl acrylate in a suitable solvent along with a monomer that is copolymerizable therewith followed by the addition of a catalyst and heating. It can also be prepared by other polymerization methods, say, the emulsion polymerization method.

As the catalyst to be used in the solution polymerization method, the radical initiators such, for example, as benzoyl peroxide, azobisisobutyronitrile and lauryl peroxide are useful. These are usually used in an amount of 0.2-2.0 percent by weight based on the total amount of the monomer. On the other hand, usable as the solvent are, for example, the esters such as methyl acetate and ethyl acetate, the aromatic hydrocarbons such as benzene, toluene and xylene, the alicyclic hydrocarbons such as cyclohexane, the halogenated hydrocarbons such as methylene chloride and ethylene dichloride, and the ketones such as acetone and methyl ethyl ketone. Of these, preferred is ethyl acetate in view of its possession of an especially suitable boiling point and the fact that the solubility of the resulting copolymer is good. A monomer concentration t the time of the polymerization reaction of 35 60 percent by weight is preferred. When the monomer concentration at the time of the polymerization reaction is less than 35 percent by weight, the polymerization speed becomes extremely slow, whereas if this concentration exceeds 60 percent by weight, the evolution of polymerization heat becomes great. Usually, with a polymerization temperature of 70 C. and a polymerization time of 5 10 hours the copolymer can be obtained at a polymerization conversion of above 95 percent.

On the other hand, when the emulsion polymerization method is employed, the monomers are usually emulsified in water and polymerized in the presence of a water-soluble polymerization initiator. The amount of water usually used in this case is preferably 0.5 3 times the total weight of the monomers. Usable as the emulsifiers are the usual emulsifiers such as sodium ,ifalkylaryl polyester sulfonates and sodium alkylarylsulfonates, while as the polymerization initiators usable are the usual water-soluble polymerization initiators such as potassium persulfate and ammonium persulfate. If in this case conjoint use is made of a reducing agent such as sodium hydrogen sulfite, the polymerization reaction can be carried out at a lower temperature and more promptly. While the polymerization conditions will vary depending upon such as the class of monomers used, the copolymer is usually readily obtained with a temperature of 20- C. and a polymerization time of l 10 hours.

The so obtained copolymer consisting predominantly of an alkyl acrylate is usually used as a solution in the esters such as methyl acetate and ethyl acetate, the aromatic hydrocarbons such as benzene, toluene and xylene, the alicyclic hydrocarbons such as cyclohexane, and the halogenated hydrocarbons such as methylene chloride and ethylene chloride. The foregoing organic solvent solution of a copolymer consisting predominantly of an alkyl acrylate is desirably used after adjusting its solids content to 25 percent by weight, and preferably percent by weight.

The adhesive composition according to the present invention is prepared, for instance, in the following manner. The organic solvent solution of a copolymer consisting predominantly of an alkyl acrylate is mixed with an aqueous hydroxyethyl cellulose solution with well stirring to prepare a homogeneous dispersion. When this mixture is directly applied to a suitable backing in customary manner and dried, a pressure-sensitive adhesive tape or sheet material having an adhesive layer consisting of a breathable adhesive composition can be prepared. Alternately, if the foregoing mixture is applied uniformly to a flat, smooth liner having a strippable surface, a breathable adhesive composition film is obtained. When the so obtained film is then transferred with pressure to a suitable backing, a breathable adhesive tape or sheet material can be prepared.

It is an advantage from the operational standpoint to use as the organic solvent solution of a copolymer consisting predominantly of an alkyl acrylate one whose solids concentration is 5 25 percent by weight, and preferably 10 l5 percent by weight.

The hydroxyethyl cellulose, used as a l 5 weight percent aqueous solution, is used with the organic solvent solution of a copolymer consisting predominantly of an alkyl acrylate in an amount such that its solids content is l 10 percent by weight, and preferably 3 7 percent by weight, of the total solids content.

As the liner having a flat, smooth surface that is used for applying the adhesive composition of this invention, the commercially available strippable paper can be used as such, but it is also possible to use the commercial stripping agent after applying same to a suitable support followed by drying.

While the thickness of the adhesive composition layer will be determined by the degree of breathability required for its intended use and the adhesive strength required, it is usually 10 40 microns, and preferably 30 microns.

In applying the invention adhesive composition mixture, the conventional roll coating machine is used.

As the substrate for use as the aforesaid backing, any will do so long as it is one having gas permeability. For instance, the perforated plastic films, cloths, nonwoven fabrics and papers can be used. Especially, in the case of the tapes and sheet materialsfor medical uses, the perforated polyethylene films and rayon nonwoven fabrics can be effectively used.

An adhesive coating which possesses excellent adhesiveness as well permits the full breathing activity of the object adhered therewith can be obtained by the use of the invention adhesive composition. For instance, as mentioned in a hereinafter given Example, an adhesive composition incorporated with about 5 percent by weight of a hydroxyethyl cellulose has a moisture-transmission rate at a temperature of 37C. and a relative humidity of 90 95 percent of l8.l mg/cm -hr when the thickness of the adhesive coating is of the order of microns (in the case where a backing having a moisture-transmission rate of 26.l mglcm -hr is used), thus achieving a moisture-transmission rate of more than four times that of the 4.3

mg/cm -hr of the case where the hydroxyethyl cellulose is not added. Hence, when the invention adhesive composition is used in preparing a surgical tape and the so prepared tape is adhered to the human body. it is very effective in preventing the irritating to the skin.

The following examples will be given for more fully illustrating the invention. The parts used in the examples are in all cases on a weight basis. The invention adhesive composition and the adhesive tape obtained by using the ordinary office stationery as backing and applying thereto the invention adhesive composition as the adhesive coating were submitted to the following performance tests and evaluated.

1. Cohesive strength of the adhesive composition.

The adhesive composition is applied to two sheets of glass, each 2.6 cm in width, 5 cm in length and 0.8 mm in thickness. After the adhesive composition has dried, the glasssheets areplaced one on top of the other in such a manner that 1.3 cm of each the adhesive layers are laid in contact with each other. The sheets are then pressed together. The 0 degree pulling test is conducted using a bonded area of 3.4 cm". Further, the thickness of the adhesive layer is adjusted to 40 microns, and the shear strength at a pulling speed of 2 cm/min. is measured, this value being used as a measure of the cohesive strength.

2. Breathability of the adhesive tape.

A moisture-transmissible aluminum cup (moisture transmission area =28.26 cm) satisfying the requirements of the 118 Method 6549 (Method for Testing the Moisture-transmissibility of Leather) is used, and measurements of the increase in weight are made at hourly intervals up to 5 hours in accordance with the procedure described in the foregoing .llS method. The amount of moisture transmission (mg) per square centimeter of moisture-transmission area per hour of moisture-transmission time (moisture-transmission rate mglcm -hr) is then obtained from the slope of the measurements and used as a measure of the breathability. As the moisture absorbing agent, 20 grams of calcium chloride dihydrate is used, and the measurements are made under the conditions of a temperature of 37C. and a relative humidity of 90 95 percent.

3. Adhesive strength of the adhesive tape.

An adhesive tape 1.0 cm in the width having an adhesive coating of 25-micron thickness is prepared by the transfer method described in Example I, using as the backing an office stationery. This adhesive tape is adhered to a stainless steel plate by application of a pressure of l kg/cm for one minute. A lpulling test is then conducted with a pulling speed of 2 cm/min. to obtain the peeling strength (g/cm), which is used as a measure of the adhesive strength.

EXAMPLE I AND CONTROL 1 A reactor equipped with a reflux condenser and a stirrer was charged with parts of 2-ethylhexyl acrylate, 7.4 parts of methyl methacrylate, 2.5 parts of methacrylic acid, 0.1 part of polyethylene glycol (degree of polymerization i4 dimethacrylate, 02 part of benzoyl peroxide and I00 parts of ethyl acetate, and the polymerization reaction was carried out for 10 hours with gentle stirring. The polymerization conversion was 99.9 percent. 624 parts of ethyl acetate was added to the resulting polymer solution, and an adhesive dope having a solids concentration of 13.8 ture of 93C. The thickness of the adhesive coating of percent (hereinafter designated dope A) was prepared. this adhesive tape was 25.5 microns, and its moisture- 41 Parts ofa 1.8 percent aqueous solution of hydroxtransmission rate was 16.2 mg/cm -hr. On the other yethyl cellulose was then added to 100 parts of the hand, its adhesive strength was 130 g/cm.

foregoing dope A to prepare an adhesive composition [t can be seen from this example that the method of dope whose hydroxyethyl cellulose content was 5 perpreparing the adhesive tape has nothing to do with its cent by weight of the total solids content (hereinafter moisture transmissibility, and that the adhesive compodesignated dope B). When the cohesive strengths of sition dope is responsible for this property.

dopes A and B were measured, there was no great difference. it was thus found that the cohesive strength EXAMPLE 3 does not drop by the addition of the hydroxyethyl cellu- An adhesive tape in which the content of the hydroxlose. yethyl cellulose in the adhesive composition was This dope B was applied to a commercial strippable percent by weight was prepared by operating exactly as paper in an amount such that the thickness of the adhein Example 1 but using 88 parts ofa 1.7 weight percent sive composition film, when dried, would become aqueous hydroxyetyl cellulose solution for each 100 about 25 microns and dried for 30 minutes at a temperparts of the same dope A as that used in Example I.

ature of 93C. At this stage, the adhesive composition is The so obtained adhesive tape had a 25.9-micron-thick completely dry and is completely devoid of volatile adhesive coating, and its moisture-transmission rate components. Next, a commercial office stationary was was l6.4 mglcm -hr, while its adhesive strength was overlaid stop this adhesive composition film and trans- 100 g/cm. Thus, the properties possessed by this adheferred and adhered thereto with the application of sive tape was excellent.

pressure. This was followed by again heat treating the adhesive composition film-adhered stationary for 30 EXAMPLE 4 minutes at 93C. The strippable paper was then re- An adhesive tape in which the content of the hydroxmoved and an office stationery-backed adhesive tape yethyl cellulose in the adhesive composition was 1.0 was thus obtained. The transmission rate and adhesive weight percent was prepared by operating exactly as in strength of this adhesive tape was then measured. Example 1 but using l5 parts of a 1.0 weight percent As control, an adhesive tape prepared in like manner aqueous hydroxyethyl cellulose solution for each 100 but using dope A not containing the hydroxyethyl celparts of the same dope A as that used in Example 1.

lulose was also measured for its transmission rate and The thickness of the adhesive coating of this adhesive adhesive strength. The results obtained in the cases of tape was 25.0 microns, while the moisture-transmission the adhesive composition containing the hydroxyethyl rate and adhesive strength of this tape were 8.2

cellulose and that not containing the hydroxyethyl celmglcm -hr and 174 g/cm, respectively. lulose are shown together in Table 1.

Table 1 Amount Thickness moisture added of of transmishydroethyl Cohesive adhesive sion rate Adhesive Dope cellulose strength coating (mglcm'- strength used (wt (g/cm) t) hr) (g/cm) Example I dope B 5.0 2960 25.0 NH 135 Control 1 dope A 0 2640 24.3 4.3 190 Commercial stationary 26. l

Example I is the case where the adhesive composi- CONTROL 2 tion containing the hydroxyethyl cellulose was used. This experiment illustrates the case where the hy- The moisture-transmission rate demonstrated in this droxyethyl cellulose was used in excess of the range case was a very excellent one of l8.l mglcm -hr, which specified by this invention. corresponds to about 70 percent of the moisture-trans- The experiment was carried out as in Example 1, mission rate of the backing alone, i.e., the case where except that 50 parts of a 4.8weight percent aqueous the office stationary is not applied the adhesive composolution of the hydroxyethyl cellulose was used for sition. On the other hand, in the case where dope A not each 100 parts of the same dope A as that used in containing the hydroxyethyl cellulose was used (Con- Example 1 to prepare a commercial office stationerytrol l), the moisture-transmission rate was only 4.3 backed adhesive tape in which the hydroxyethyl cellumg/cm -hr, a value less than one-fourth of that of Exlose content in the adhesive composition was about l5 ample l, in spite of the fact that the thickness of the percent by weight. While the so obtained adhesive adhesive coating was about the same. tape, whose thickness of the adhesive coating was 24.8 While the adhesive strength of the adhesive tape of microns, had an excellent moisture-transmission rate of Example 1 is 135 g/cm, this is adequate for ordinary 17.2 mg/cm -hr, it was of no practical use, since its purposes. adhesive strength was too low, being only g/cm.

EXAMPLE 2 CONTROL 3 An adhesive tape was prepared by uniformly apply- 65 Example I was repeated, except that 7 parts ofa l.0 ing the same dope B as that used in Example I to an weight percent aqueous hydroxyethyl cellulose solution office stationery of the same type as that used in Examwas used for each parts of the same dope A as that ple 1. followed by drying for 30 minutes at a temperaused in Example I to prepare a commercial office stationary-backed adhesive tape in which the hydroxylethyl cellulose content in the adhesive composition was about 0.5 percent by weight. The thickness of the adhesive coating of the so obtained adhesive tape was 24.7 microns. On the other hand, while this adhesive tape had an excellent adhesive strength of I85 g/cm, its moisture-transmission rate was only 6.5 mg/cm -hr, and hence this ,tape could not possibly be called a breathable adhesive tape.

5 positions could possibly by considered as being a breathable adhesive composition.

EXAMPLES 5 8 Adhesive compositions of varied compositions were 10 re ared by erating as in Example I but varying the CONTROLS 4 17 lasses and amzunts of the monomers used. The results These experiments illustrate that adhesive composiobtained are shown in Table 3. In all instances the tions having an adequate moisture transmissiblity canamount of the hydroxyethyl cellulose was percent by not be obtained even though water-soluble or hydroweight of the total solids content. As is apparent from philic polymers other than hydroxyethyl cellulose are Table 3, the compositions of Examples 5 8 demonadded to the copolymer consisting predominantly of alkyl acrylates.

strated in all cases satisfactory moisture-transmission rate as well as adhesive strength.

Table 3 Copolymer composition Thick Polyethyness Moisture lene of adtransmi- 2- glycol hesive ssion Ethylhexyl Vinyl Methacrydimethacoatrate Adhesive acrylate acetate lic acid crylate ing (mg1/cm*- strength (parts) (parts) (parts) (part) (p) r) (g/cm) Example 5 90.0 7.5 2.5 0.05 20.7 14.7 F Example 6 97.5 2.5 0.05 l9.5 16.4 180 Example 7 75.0 25.0 22.2 13.1 204 Example Various water-soluble or hydrophilic polymers were We claim:

mixed with the same dope A as that used in Example I, the water-soluble ones being used as aqueous solution and the water-insoluble ones being used as organic solvent solutions. Then by operating as in Example 1 adhesive tapes having a commercial office stationary as backing were prepared. Further, adhesive tapes having adhesive coatings of varied thickness were prepared as in Control I.

These tapes were measured for their adhesive coating thickness and moisturetransmission rate, with the re- I. An adhesive composition comprising, of the total composition of I00 parts by weight, 90 99 parts by weight of a tacky copolymer obtained by copolymerizing a. 75 95 mol percent of at least one alkyl acrylate,

40 the alkyl group of which contains 1 to l4 carbon atoms and the average number of which carbon atoms is 4 to l2, or a mixture of at least one class of said alkyl acrylate with methyl methacrylate and/or vinyl acetate in a molar ratio of 5 or more to sults shown in Table 2. 45 l; with Table 2 Thickness Moisture Additive ol' permeaadhesive ture coating speed (m cm- Class wt% Solvent (1.) r)

Control 4 cellulose acetate 10.0 Acetone 29.0 .1 Control 5 meth lcellulose 15.0 Water 2L0 6.7 Control 6 ethy cellulose 15.0 Acetone 21.0 5.0 Control 7 hydroxypro yl cellulose 10.0 Water 30.l 5.3 Control 8 carboxymet yl cellulose l5.0 Water 20.3 7.5 Control 9 cellulose acetate terephthalate l0.0 Acetone 30.6 3.5 Control 10 polyethylene glycol l0.0 Methyl- 28.9 4.5

lene chloride Control ll pol vinyl pyrolidone [5.0 Water 22.] 6.9 Control l2 SOCflUlTl pol acrylate l5.0 Water 22.6 4.8 Control l3 polyacry amide l0.0 Water 26.2 4.8 Control 14 [4.2 7.0 Control 15 24.3 4.3 Control 16 27.5 3.5 Control 17 40.9 2.8

While Controls 4 13 were in all cases those in which either a water-soluble or hydrophilic polymer was used b. 5 mol percent of acrylic acid and/or methacrylic acid, and I0 1 parts by weight ofa hydrox- 

1. AN ADHESIVE COMPOSITION COMPRISING, OF THE TOTAL COMPOSITION OF 100 PARTS NY WEIGHT, 90-99 PARTS BY WEIGHT OF A TACKY COPOLYMER OBTAINED BY COPOLYMERIZING A. 75-95 MOL PERCENT OF AT LEAST ONE ALKYL ACRYLATE, THE ALKYL GROUP OF WHICH CONTAINS 1 TO 14 CARBON ATOMS AND THE AVERAGE NUMBER OF WHICH CORBON ATOMS IS 4 TO 12, OR A MIXTUE OF AT LEAST ONE CLASS OF SAID ALKYL ACRYLATE WITH METHYL METHACRYLATE AND/OR VINYL ACETATE IN A MOLAR RATIO OF 5 OR MORE TO 1; WITH N. 5-25 MOL PERCENT OF ACRYLIC ACID AND/OR METHACRYLIC ACID, AND 10-1 PARTS NY WEIGHT OF A HYDROXYETHYL CELLULOSE.
 2. An adhesive composition of claim 1 wherein said copolymer is that obtained by copolymerizing a. 94 - 98 mol percent of at least one alkyl acrylate, the alkyl group of which contains 1 to 14 carbon atoms and the average number of which carbon atoms is 4 to 12, or a mixture of at least one class of said alkyl acrylate with a member selected from the group consisting of methyl methacrylate, vinyl acetate and mixtures thereof in a molar ratio of 5 or more to 1; b. 2 - 6 mol percent of a member selected from the group consisting of acrylic acid, methacrylic acid and a mixture thereof; and c. 0.002 - 0.05 mol percent of a compound selected from the group consisting of diallyl phthalate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolethane trimethacrylate and pentaerythritol tetra methacrylate.
 3. An adhesive composition of claim 1 wherein said alkyl acrylate is 2-ethylhexyl acrylate. 